The invention relates to the packaging and handling of corrugated sheet material, and more particularly, to a method and apparatus for automatically stacking corrugated sheets into bundles, forming the bundles into tiers, and stacking the tiers into block shaped units of optimal size.
Mechanical bundle/tier/unit stacking systems are known in the art, but are relatively inefficient. One particular problem with such prior art systems is that when an order is to be run on a corrugator, an operator must make an initial determination of how many corrugated sheets should form a bundle, and how many bundles should form a tier, and how many tiers should form a unit to accommodate the total order of corrugated sheets placed. These initial determinations by the operator must take into consideration such things as the number of total corrugated sheets ordered, and the width and length of each of the corrugated sheets. These operator determinations usually result in an end unit that is not flat and therefore, is difficult to band.
It is also very difficult for such a system to produce units of a predetermined size. For example, a customer may wish to place an order of corrugated sheets and have them delivered in units of a desired size. On a fast paced corrugated production line, it is not possible for a scheduler, or an operator, to take the time and slow down the production line to calculate how best to arrange the bundles, and how many sheets to place in each bundle to satisfy such a desired result. Further, these prior art systems do not take into account the number of outs from the corrugator. For example, a particular order may be scheduled as a four-out on the corrugator, but the customer would like the unit to be delivered with a maximum width of three bundles. This would require load-breaking the bundles just discharged from the stacker and re-accumulating the bundles into the appropriate units. This not only requires operator intervention, but also significantly slows the production line. It has been found that this is particularly difficult to do with short and narrow sheets. Further, at the end of an order, it is likely that there will be leftover bundles requiring the operator to manually form a level tier from the leftover bundles.
It has also been found that the aesthetic look of a unit in terms of sheet-to-sheet alignment is important because this is the product that sheet feeder corrugators sell. Further, misaligned sheets can be damaged when banding or handling which can result in a significant percentage of returned goods to the plant. It has also been found that short and narrow sheets are very difficult to run and achieve good stacking quality. It would be desirable for a sheet feeder corrugator to produce units of very well-aligned sheets, which would give producers a way of differentiating their product in the marketplace.
It would also be desirable to have a system that optimizes the unit construction by simply inputting the total number of sheets ordered, the sheet size, and have the ability to consider the number of outs scheduled on the corrugator, as well as other criteria if the customer so desires.